1. Field of the Invention
The invention concerns a method for determining the glucose concentration in tissue fluid in which test values for glucose and for an endogenous reference substance are detected in a sample liquid obtained from a body tissue by microdialysis, microperfusion or ultrafiltration and the test value for glucose is corrected in accordance with the test value for the reference substance. The invention also concerns a corresponding device.
2. Description of the Prior Art
Body tissue consisting of cells in a liquid environment in which metabolic products are transported between the cells and the blood vessels. In order to monitor glucose of diabetic patients, for example, it is possible to insert a probe into tissue for long periods in order to continuously obtain components from the tissue fluid by means of diffusion processes and to determine the glucose content in the tissue from the effusate. This can correlate closely with the blood glucose content without requiring an invasive access to the blood circulation. The measurement can take place outside of the body in which case the sample liquid is applied to a sensor. In this connection an ionic reference technique is known in which an ionic reference value and in particular Na+ is detected simultaneously with glucose by an ion-selective electrode in order to calibrate the recovery of the glucose in the dialysate. In this case, it is assumed that the known concentration of the reference substance in the body fluid is substantially invariant. A prerequisite of the known evaluation methods is that there is a strict linear relationship between the recovery of the endogenous calibrator and glucose in the sample liquid. However, empirical comparative measurements make this seem doubtful.